Vog is a combination of the words "volcanic" and "smog" and is used to describe the air pollution created by outgassing from volcanoes. It's a word everyone in the Hawaiian islands recognises, especially those of us who live on the Big Island of Hawai`i. It's a serious health concern as well as a threat to crops downwind from the volcano. With Kilauea being so active these days the vog has been the worst many people can remember. Well over 2,000 tonnes of sulphur dioxide is being pumped out of Kilauea into the atmosphere each day, several times the "normal" amount. On some days the smell of sulphur is quite pervading.
The panorama above was taken from the top of Mauna Kea a couple of days ago after the trade winds had just started to return to the islands. Mauna Loa is the mountain in the distance and to get your bearings, east is to the left and south is straight ahead. The trades cleared out the east side of the island but the vog remained elsewhere - it's the murky grey and white crud visible at lower altitudes, although it has been reaching summit level quite frequently recently, which is very rare.
Kilauea isn't in the shot, in fact you can't see it from this exact location as it's hidden by Mauna Kea's summit, but if you could it would be about a photo's width to the left. Last week, Andrew posted a picture of the island taken by the crew of of the space shuttle Atlantis which might give you a better picture of the geography of the island and the vog. It's well worth a look!